Reactions of PdCl2 with 2 equiv of N,N′-disubstituted-imidazole-2-thiones R1R2C3N2S (R1 = R2 = Me (1a), iPr (1b), Cy (1c), C6Me3H2 (1d); R1 = Me, R2 = Ph (1e)) under the different conditions afford five mononuclear complexes trans-[(R1R2C3N2S)2PdCl2] (R1 = R2 = Me (2a), iPr (2b), Cy (2c), C6Me3H2 (2d); R1 = Me, R2 = Ph (2e)) and five binuclear Pd(II) complexes [(PdCl2){μ-(R1R2C3N2S)}]2 (R1 = R2 = Me (3a), iPr (3b), Cy (3c), C6Me3H2 (3d); R1 = Me, R2 = Ph (3e)), respectively. Complexes 2a–2e are easily converted into the corresponding 3a–3e by adding equimolar PdCl2 in refluxing MeOH, while the reverse reaction is achieved at room temperature by addition of 2 equiv of 1a–1e. In 2b, 2d, and 2e, each Pd(II) holds a distorted square planar geometry completed by two trans Cl atoms and two trans S atoms. Complexes 3a–3e have a dimeric [Pd2S2] structure in which two {PdCl2} units are interlinked by two N,N′-disubstituted-imidazole-2-thiones. Each Pd(II) adopts a distorted square planar geometry accomplished by two cis Cl atoms and two cis bridging S atoms. Among them, complex 3d has the two largest C6Me3H2 groups on the 2 and 5 positions of imidazole-2-thione, the longest Pd−μ-S bond, the largest S–Pd–S angle, and displays the highest catalytic activity toward Suzuki–Miyaura and copper-free Sonogashira cross-coupling reactions, which are confirmed by density functional theory calculations. The results provide an interesting insight into the introduction of various substituent groups into the periphery ligands of coordination complex-based catalysts, which could tune their geometric structures to acquire the best catalytic activity toward organic reactions.

Solvothermal reactions of Zn(NO3)2·6H2O with 1,4-bis(2-(pyridin-4-yl)vinyl)naphthalene (1,4-bpyvna) and 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC) (molar ratio = 1:1:1) at 120 °C in CH3CN/H2O (v/v = 1:2) afforded one three-dimensional (3D) coordination polymer [Zn2(1,4-bpyvna)(1,3,5-HBTC)2(H2O)]n (1). Similar reactions with the same three components at 140 °C in dimethylformamide (DMF)/CH3CN/H2O produced another 3D coordination polymer {[Zn2(1,4-bpyvna)(1,3,5-BTC)(OH)]·H2O}n (2) in 72% yield. When the molar ratio of Zn(NO3)2·6H2O, 1,4-bpyvna, and 1,3,5-H3BTC was changed to 1:1:2, the analogous treatment at 140 °C yielded one one-dimensional coordination polymer {[Zn(1,3,5-HBTC)2(H2O)][1,4-bpyvna-H2]·CH3CN}n (3, 1,4-bpyvna-H2 = 4,4′-((1,1′)-naphthalene-1,4-diylbis(ethene-2,1-diyl))bis(pyridin-1-ium)). Solvothermal reactions of Zn(NO3)2·6H2O with equimolar 1,4-bpyvna and 1 or 2 equiv of 4,4′-oxidibenzoic acid (4,4′-H2OBA) at 120 °C in DMF/CH3CN/hexane resulted in the formation of {[Zn2(1,4-bpyvna)(4,4′-OBA)2]·0.5DMF·2.25H2O}n (4) and {[Zn2(1,4-bpyvna)(4,4′-OBA)2]·3DMF}n (5), respectively. Compounds 1–5 were characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction, and thermogravimetric analysis. Upon addition of Hg2+ ions to the DMF solution of 1,4-bpyvna, remarkable changes in the absorbance and emissive spectra were observed, associated with color changes, which were easily identified by the naked eye. This ligand could serve as a chemoprobe with the detection limit of Hg2+ being 0.060 ppm. When solid 2 was added in the DMF solution containing Hg(NO3)2, the emission color of 2 was also changed from blue to yellow, and its detection limit of Hg2+ was as low as 0.057 ppm. This compound can be reused for several cycles without evident efficiency decay. Compound 2 would be a promising sensitive naked-eye indicator for low-concentration Hg2+ with high sensitivity and selectivity.

RuCl3 efficiently catalyzes the alkylation of methylquinolines, methylpyridines, 2-methyl-benzooxazoles, and 2-methyl-quinoxalines with alkyl- or aryl-alcohols as alkylating agents. This synthetically useful and atom economical transformation does not require additional ligands. The mechanistic study indicated the alkylation reaction underwent a stepwise transfer hydrogenation, aldol condensation, and hydrogenation reaction pathway.

Reactions of Cd(NO3)2·4H2O with 1,2,4,5-tetrakis(4-pyridylvinyl)benzene (4-tkpvb) and 5-tert-butylisophthalic acid (5-tert-H2BIPA), 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC) or 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) under solvothermal conditions afforded three two-dimensional (2D) Cd(II) coordination polymers [Cd(4-tkpvb)(5-tert-BIPA)]n (1), [{Cd(4-tkpvb)(1,3,5-HBTC)}·0.5DMF]n (2) and [Cd(4-tkpvb)(1,4-NDC)]n (3). Compounds 1–3 were structurally characterized by IR, elemental analysis, powder X-ray diffraction, and single crystal X-ray diffraction. Compounds 1–3 possess unique 2D networks in which 1D double chains [Cd2L2]n (L = 5-tert-BIPA or 1,3,5-HBTC) (1–2) or 1D linear chains [Cd(1,4-NDC)]n (3) are linked by 4-tkpvb ligands. Upon UV light excitation, a 4-tkpvb solution in DMF showed an emission band centered at 446 nm with a shoulder at 475 nm. The addition of Hg2+ ions into the 4-tkpvb solution in DMF remarkably changed its colour from colourless to yellow under natural light, or from blue to grey yellow under UV light, which were clearly visible to the naked eye. Compounds 1–3 suspended in water could emit yellow-green light under UV light irradiation. The representative compound 1 was confirmed to be an uncommon multi-responsive luminescent sensor for Hg2+, CrO42− and Cr2O72− ions in water by the luminescence quenching method. The detection limits for these species were 0.15 μM (Hg2+), 0.08 μM (CrO42−) and 0.12 μM (Cr2O72−), respectively. The luminescence quenching mechanism studies revealed that these quenching processes were involved in either the interaction of Hg2+ with free pyridyl groups in 1 or the overlap between the absorption band of CrO42− or Cr2O72− and the excitation and/or emission bands of 1.

Solvothermal reactions of Cd(NO3)2·4H2O with 4-pyr-poly-2-ene (ppene) in the presence of benzene-1,2-dicarboxylic acid (1,2-H2BDC), benzene-1,3-dicarboxylic acid (1,3-H2BDC), benzene-1,4-dicarboxylic acid (1,4-H2BDC), benzene-1,3,5-tricarboxylic acid (1,3,5-H3BTC), or 4,4′-oxidibenzoic acid (4,4′-H2OBA) afforded five Cd(II) coordination polymers [Cd(ppene)(1,2-BDC)]n (1), [Cd(ppene)(1,3-BDC)]n (2), [{Cd(ppene)(1,4-BDC)}·MeCN]n (3) (Liu et al. Inorg. Chem. Commun. 2015, 58, 1−4), [{Cd(ppene)(1,3,5-HBTC)}·0.5(ppene)]n (4), and [Cd(ppene)(4,4′-OBA)]n (5), respectively. Upon UV light irradiation, 1, 3, and 4 can undergo a double [2 + 2] cycloaddition reaction to yield their corresponding photoproducts including [Cd2(4-tp-3-lad)(1,2-BDC)2]n (1a, 4-tp-3-lad = 2,3,5,6-tetra(pyridin-4-yl)bicyclo[2.2.0]hexane), [{Cd2(4-tp-3-lad)(1,4-BDC)2}·2MeCN]n (3a), and [{Cd2(4-tp-3-lad)(1,3,5-HBTC)2}·(ppene)]n (4a) in a single-crystal-to-single-crystal manner. Compounds 1, 2, 4, 5, 1a, 3a, and 4a have been structurally characterized by elemental analysis, infrared spectroscopy, powder X-ray diffraction, and single-crystal X-ray diffraction. Compounds 1, 1a, 4 and 4a consist of two-dimensional (2D) (4,4) networks, in which one-dimensional (1D) [Cd2(1,2-BDC)2]n or [Cd2(1,3,5-HBTC)2]n chains are linked by ppene or 4-tp-3-lad bridges. 2 has a three-dimensional (3D) 3-fold interpenetrated framework formed from bridging 1D [Cd2(1,3-BDC)2]n double chains by ppene ligands. Compounds 3a and 5 contain 3D frameworks assembled by linking 2D [Cd2(1,4-BDC)2]n or [Cd2(4,4′-OBA)2]n networks by 4-tp-3-lad or ppene bridges. In the three photoreactions, each ppene ligand had its two conjugated C═C bonds parallel to those of the neighboring ppene. The resulting ppene pair was transformed into the only product, 4-tp-3-lad, through a unique double [2 + 2] cycloaddition. Photoluminescence properties of these compounds in water were also investigated. Compound 3a as a representative example was proven to be an efficient probe for dual detections of nitroaromatics and Hg2+ in aqueous solutions.

A series of ((pyridinyl)-1H-pyrazolyl)pyridine (pypzpy) ligands in which the pyrazolyl ring at 1- and 3-positions is modified by two 2-, 3-, or 4-pyridyl groups were prepared. Reaction of CuI with 2-(1-(pyridin-2-yl)-1H-pyrazolyl)pyridine (2,2′-pypzpy) in MeCN at room temperature or solvothermal reaction of the same components at 120 °C afforded one binuclear complex [{(2,2′-pypzpy)Cu}(μ-I)]2 (1). Treatment of CuI with 3-(1-(pyridin-2-yl)-1H-pyrazolyl)pyridine (3,2′-pypzpy) at room temperature or at 120 °C produced one-dimensional (1D) polymer [{Cu3(μ3-I)3}(μ-3,2′-pypzpy)]n (2) and one two-dimensional (2D) polymer [{Cu2(μ-I)(μ3-I)}2(3,2′-pypzpy)2]n (3), respectively. Similar reactions of CuI with 4-(1-(pyridin-2-yl)-1H-pyrazolyl)pyridine (4,2′-pypzpy) at room temperature or at 150 °C yielded one 1D polymeric complex [{Cu(μ3-I)}2(4,2′-pypzpy)2{Cu(μ-I)}2]n (4). Complexes [{Cu3(μ3-I)3}(μ-2,3′-pypzpy)]n (5), [(CuI)(μ-2,3′-pypzpy)]2 (6), [(Cu2I2)(3,3′-pypzpy)] (7), [(CuI)(4,3′-pypzpy)] (8), [{Cu(μ3-I)}2(μ-2,4′-pypzpy)2{Cu(μ-I)}2]n (9), [(CuI)(3,4′-pypzpy)] (10), and [(CuI)(μ-4,4′-pypzpy)]n (11) could be isolated by solution reactions or solvothermal reactions of CuI with 2-, 3-, 4-(1-(pyridin-3-yl)-1H-pyrazolyl)pyridine (2,3′-, 3,3′-, 4,3′-pypzpy), or 2-, 3-, 4-(1-(pyridin-4-yl)-1H-pyrazolyl)pyridine (2,4′-, 3,4′-, 4,4′-pypzpy). Compounds 1–11 were characterized by IR, elemental analysis, powder X-ray diffraction, and single-crystal X-ray crystallography. Complex 1 contains a normal [Cu(μ-I)]2 dimeric structure. Complexes 2 and 5 consist of a unique displaced staircase chain [Cu2(μ3-I)2]n. Complex 3 has a 2D network formed by linking chairlike [Cu2(μ-I)(μ3-I)]2 units with two pairs of 3,2′-pypzpy bridges. Complexes 4 and 9 have a rare 1D triple chain, in which one internal 1D ladder-like chain [Cu2(μ3-I)2]n is connected with two zigzag chains [Cu(μ-I)]n via 4,2′-pypzpy or 2,4′-pypzpy ligands. Compound 6 consists of two [CuI] units interconnected by two 2,3′-pypzpy ligands. Compound 11 contains a 1D chain assembled by monomeric [CuI] units and 4,4′-pypzpy ligands. The luminescence properties of 1–11 in solid state were also investigated at room temperature. These results offer an interesting insight into how the coordination sites of the pypzpy ligands do exert great impact on their coordination modes, the coordination spheres of the Cu(I) centers, the formation of the [CunIn] motifs and the topological structures of the final complexes.

Four different types of TEMPO derivatives incorporated with an ionic liquid moiety and N,N-bidentate coordination group (IL–TEMPO-N,N) were prepared. The CuBr/IL–TEMPO-N,N system showed high catalytic activity toward the synthesis of aldehydes and imines via the aerobic oxidation of alcohols in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4). Both the Cu catalyst and IL–TEMPO-N,N co-catalyst in homogeneous catalytic systems could simultaneously be recovered from the products by extraction using Et2O. The remaining catalyst system in the ionic liquid phase could be reused for several cycles without obvious loss of catalytic activity. Protocols for highly efficient and recyclable aerobic oxidation of alcohols to aldehydes and imines were established.

Without using any additional ligands, RuCl3 efficiently catalyses the reductive N-alkylation of aryl nitro compounds with alcohols using bio-based glycerol as the hydrogen source and without the need for any added solvents. The reaction can be easily manipulated to produce either imines or secondary amines in high yields. RuCl3-catalyzed reductive N-alkylation of nitroarenes with alcohols affords the corresponding imine products in good to excellent yields. Under the same reaction conditions, the one-pot sequential reaction of nitroarenes with alcohols and glycerol also gives amines in higher yields.

Four anionic ligands including 1-methyl-3(or 4)-(1-(pyridin-2-yl)-1H-pyrazol-3-yl)pyridin-1-ium iodide ([3,2′-pypzpym]I, [4,2′-pypzpym]I) and 1-methyl-3(or 4)-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)pyridin-1-ium iodide ([2,3′-pypzpym]I, [2,4′-pypzpym]I) are prepared. Reaction of CuI with [3,2′-pypzpym]I affords a mononuclear complex [CuI2(3,2′-pypzpym)] (1) and a one-dimensional coordination polymer [(Cu4I6)(3,2′-pypzpym)2]n (2). Analogous reactions of CuI with [4,2′-pypzpym]I, [2,3′-pypzpym]I or [2,4′-pypzpym]I yield [Cu4I6(4,2′-pypzpym)2] (3), [CuI2(2,3′-pypzpym)] (4) and [CuI2(2,4′-pypzpym)] (5), respectively. Relative to that of CuI, complexes 1–5 exhibit enhanced catalytic activities towards the Chan–Lam cross-coupling reactions of imidazole and arylboronic acids in a H2OMeCN (v/v=2:1). This catalytic system is involved in the CN cross-coupling reaction and works for a variety of imidazole derivatives as well as arylboronic acids with different electronic properties.

Reactions of a pincer ligand 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine (pzpypzH) with Cu(NO3)2, Cu(ClO4)2, CuSO4, CuCl2 or CuI produced three dinuclear Cu(II) complexes [{Cu(NO3)}(μ-pzpypz)]2 (1), [{Cu(ClO4)}(μ-pzpypz)]2 (2), [Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH (3·2MeOH), one mononuclear Cu(II) complex [CuCl2(pzpypzH)] (4) and one trinuclear Cu(I)/Cu(II) complex [(ICu)(μ-I)2Cu2(μ-pzpypz)2] (5), respectively. Treatment of 4 with two equiv. of AgNO3 in DMF also gave rise to 1. Complexes 1–5 were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 or 2 has a dimeric structure in which two {Cu(X)} (X = NO3, ClO4) fragments are interconnected by two μ-pzpypz− ligands. 3 also adopts a dimeric structure in which two Cu(II) centers are interconnected by a pair of μ-pzpypz− ligands and one μ-SO42− ion. The Cu(II) center in 4 is five-coordinated by three N atoms of the pzpypzH ligand and two Cl atoms. In 5, two Cu(II) centers are bridged by two μ-pzpypz− ligands and one CuI32− unit, forming a unique trinuclear structure. Complexes 1–5 displayed high catalytic activity toward the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes in H2O. The nitrile or aldehyde products could be readily separated from the catalytic system by extraction and the residual aqueous solution containing 1 retained good activity for several cycles.

The reaction of FeCl3 with a pincer ligand, 2,6-di(1H-pyrazol-3-yl)pyridine (bppyH2), produced a mononuclear Fe(III) complex [Fe(bppyH2)Cl3] (1), which could be reduced to the corresponding Fe(II) dichloride complex [Fe(bppyH2)Cl2] (2) by suitable reducing agents such as Cp2Co or Fe powder. 1 and 2 exhibited a reversible transformation from each other with appropriate redox reagents. 1 could be utilized as a pre-catalyst to initiate the ring-opening polymerization of ε-caprolactone in the presence of alcohol but 2 did not work. The 1/alcohol system displayed characteristics of a well-controlled polymerization with the resulting poly(ε-caprolactone) having low molecular weight distributions, a linear tendency of molecular weight evolution with conversion, and polymer growth observed for the sequential additions of ε-caprolactone monomer to the polymerization reaction. The polymerization was completely turned off by the in situ reduction of the catalytic Fe center via Cp2Co and then turned back upon the addition of [Cp2Fe]PF6. The rate of polymerization was modified by switching in situ between the Fe(III) and Fe(II) species.

Reactions of 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetic acid (pypzacacH) ligand with Cu(OAc)2, Cu(NO3)2, CuSO4, Cu(ClO4)2 or CuCl2 produced four dinuclear Cu(II) complexes [{(MeOH)Cu(OAc)}(μ-κ2:κ1-pypzacac)]2·0.5H2O (1·0.5H2O), [{Cu(pypzacac)}(μ-κ2:κ1-pypzacac)2{Cu(H2O)2}](NO3)·2(MeOH)0.5·6H2O (2·2(MeOH)0.5·6H2O), [{(MeOH)Cu(mpypzacac)}(μ-SO4)]2·2MeOH (3·2MeOH; mpypzacac = methyl 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetate), [{Cu(mpypzacac)2}(μ-κ2:κ1-pypzacac){Cu(mpypzacac)}](ClO4)3·MeOH (4·MeOH) and one polymeric Cu(II) complex [(CuCl)(μ-κ3:κ1-pypzacac)]n (5), respectively. The mpypzacac ligand in 3 and 4 was in situ generated via the Cu2+-catalyzed dehydrative esterification of acetic acid of the pypzacacH ligand. Complexes 1–5 are characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 contains two {(MeOH)Cu(OAc)} fragments that are interconnected by two μ-κ2:κ1-pypzacac− ligands, forming a dimeric structure. In 2, {Cu(pypzacac)} and {Cu(H2O)2} units are bridged by a pair of μ-κ2:κ1-pypzacac− ligands. In 3, two {Cu(mpypzacac)} fragments are linked by two μ-κ1:κ1-SO42− ions to form a dinuclear structure. Complex 4 also adopts a dimeric structure in which {Cu(mpypzacac)2} and {Cu(mpypzacac)} units are interconnected by one μ-κ3:κ1-pypzacac− ligand. Complex 5 contains a 1D chain in which (CuCl) fragments are interlinked by μ-κ3:κ1-pypzacac− ligands. Complexes 1–5 exhibited excellent catalytic performance in the ammoxidation of alcohol to nitrile and the aerobic oxidation of alcohol to aldehyde in water. The catalytic aqueous solution was easily separated and could be reused for several cycles without any obvious decay of catalytic efficiency.

The Cu(I)-mediated C–S bond cleavage of 5-methyl-4-(p-tolyl)pyrimidine-2-thiol (mtpmtH) gave one 30-nuclear cluster [Cu30I16(mtpmt)12(μ10-S4)], one polymeric complex [(bmtpms)Cu-(μ-I)]n and one tetranuclear complex [(bmptmds){Cu(μ-I)}2]2; the 30-nuclear cluster displayed excellent catalytic performances in the coupling reactions of N-heterocycles and arylboronic acids and could be recycled and reused.

Reaction of Cu(OAc)2·H2O and 1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (Hdcmpz) in MeOH at room temperature afforded one tetranuclear Cu(II)/pyrazolate complex [{Cu2(μ-OAc)2}2(μ-dcmpz)2(μ-OAc)2] (1) in 89% yield. The similar reaction in refluxing MeOH produced a hexanuclear metallamacrocyclic Cu(II)/pyrazolate complex [{Cu(μ-dcmpz)}2(μ-OMe)2]3 (2) in 85% yield. Treatment of the same components under solvothermal conditions resulted in the formation of another tetranuclear Cu(II)/pyrazolate/carboxylate complex [{Cu(MeOH)}4(μ-mcccpz)4] (3, Hmcccpz = 5(3)-(methoxycarbonyl)-1H-pyrazole-3(5)-carboxylic acid) in 30% yield. The mcccpz2− ion in 3 was in situ generated via the hydrolysis of one of two esters on dcmpz ligand. Complexes 1–3 were characterized by elemental analysis, IR and single-crystal X-ray diffraction. An X-ray analysis revealed that 1 contains two {Cu(μ-OAc)}2 fragments that are interconnected by two μ-η2,η2-dcmpz− ligands and two μ-η1,η1-OAc− ions, forming a unique tetrameric structure. Complex 2 is composed of three {Cu(μ-dcmpz)}2 fragments linked by three pairs of μ-OMe− anions, forming a metallamacrocyclic crown structure. 3 consists of four {Cu(MeOH)} fragments linked by two pairs of μ-η1,η2-mcccpz2− ligands, forming a tetrameric [2 × 2] grid-like structure. Complexes 1–3 displayed high catalytic activity toward the condensation of nitriles with 2-aminoalcohol under solvent-free conditions to produce various 2-oxazolines.

Reactions of CuI with bis(4-phenylpyrimidine-2-thio)alkane ligands with different spacer lengths, [(phpy)(CH2)n(phpy)] (phpyH = 4-phenylpyrimidine-2-thiol; n = 1, bphpym; n = 2, bphpye; n = 3, bphpypr; n = 4, bphpyb; n = 5, bphpyp; n = 6, bphpyh), afforded a set of six [CunIn]-based coordination polymers, [{Cu(μ3-I)}2(phpym)]n (1), [{Cu(μ3-I)}4(bphpye)]n (2), [{(MeCN)Cu3(μ-I)2(μ4-I)}2(bphpypr)2]n (3), [{((MeCN)Cu)(μ-I)}2(bphpyb)]n (4), [{Cu2(μ-I)(μ3-I)}2(bphpyp)2]n (5) and [{((MeCN)Cu)(μ3-I)}2{Cu(μ-I)}2(bphpyh)2]n (6), respectively. Compounds 1–6 were characterized by elemental analysis, IR and single-crystal X-ray crystallography. 1 and 2 consist of an unique 2D network in which the 1D staircase [Cu2I2]n chains are linked by phpym or phpye ligands via the μ-η1(N)-η1(N) or μ-η1(N),η1(S)-η1(N),η1(S) coordination modes, respectively. Complexes 3 and 5 consist of double butterfly-shaped {(MeCN)Cu3(μ-I)2(μ4-I)}2 units or chair-like [Cu2(μ-I)(μ3-I)]2 units that are linked to their neighboring ones by pairs of bphpypr or bphpyp bridges to form a 1D double chain. 4 contains a 1D zigzag chain assembled by dimeric [{(MeCN)Cu}(μ-I)]2 cores and bphpyb ligands. In 6, unique 1D tandem-rhomboid [Cu2I2]n chains are connected by dphpyh ligands to form a 2D staircase network. In addition, the photoluminescent properties of 1–6 in the solid state at ambient temperature were investigated.

The Cu(I)-mediated C–S bond cleavage of 5-methyl-4-(p-tolyl)pyrimidine-2-thiol (mtpmtH) gave one 30-nuclear cluster [Cu30I16(mtpmt)12(μ10-S4)], one polymeric complex [(bmtpms)Cu-(μ-I)]n and one tetranuclear complex [(bmptmds){Cu(μ-I)}2]2; the 30-nuclear cluster displayed excellent catalytic performances in the coupling reactions of N-heterocycles and arylboronic acids and could be recycled and reused.

The reaction of FeCl3 with a pincer ligand, 2,6-di(1H-pyrazol-3-yl)pyridine (bppyH2), produced a mononuclear Fe(III) complex [Fe(bppyH2)Cl3] (1), which could be reduced to the corresponding Fe(II) dichloride complex [Fe(bppyH2)Cl2] (2) by suitable reducing agents such as Cp2Co or Fe powder. 1 and 2 exhibited a reversible transformation from each other with appropriate redox reagents. 1 could be utilized as a pre-catalyst to initiate the ring-opening polymerization of ε-caprolactone in the presence of alcohol but 2 did not work. The 1/alcohol system displayed characteristics of a well-controlled polymerization with the resulting poly(ε-caprolactone) having low molecular weight distributions, a linear tendency of molecular weight evolution with conversion, and polymer growth observed for the sequential additions of ε-caprolactone monomer to the polymerization reaction. The polymerization was completely turned off by the in situ reduction of the catalytic Fe center via Cp2Co and then turned back upon the addition of [Cp2Fe]PF6. The rate of polymerization was modified by switching in situ between the Fe(III) and Fe(II) species.

Reaction of Cu(OAc)2·H2O and 1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (Hdcmpz) in MeOH at room temperature afforded one tetranuclear Cu(II)/pyrazolate complex [{Cu2(μ-OAc)2}2(μ-dcmpz)2(μ-OAc)2] (1) in 89% yield. The similar reaction in refluxing MeOH produced a hexanuclear metallamacrocyclic Cu(II)/pyrazolate complex [{Cu(μ-dcmpz)}2(μ-OMe)2]3 (2) in 85% yield. Treatment of the same components under solvothermal conditions resulted in the formation of another tetranuclear Cu(II)/pyrazolate/carboxylate complex [{Cu(MeOH)}4(μ-mcccpz)4] (3, Hmcccpz = 5(3)-(methoxycarbonyl)-1H-pyrazole-3(5)-carboxylic acid) in 30% yield. The mcccpz2− ion in 3 was in situ generated via the hydrolysis of one of two esters on dcmpz ligand. Complexes 1–3 were characterized by elemental analysis, IR and single-crystal X-ray diffraction. An X-ray analysis revealed that 1 contains two {Cu(μ-OAc)}2 fragments that are interconnected by two μ-η2,η2-dcmpz− ligands and two μ-η1,η1-OAc− ions, forming a unique tetrameric structure. Complex 2 is composed of three {Cu(μ-dcmpz)}2 fragments linked by three pairs of μ-OMe− anions, forming a metallamacrocyclic crown structure. 3 consists of four {Cu(MeOH)} fragments linked by two pairs of μ-η1,η2-mcccpz2− ligands, forming a tetrameric [2 × 2] grid-like structure. Complexes 1–3 displayed high catalytic activity toward the condensation of nitriles with 2-aminoalcohol under solvent-free conditions to produce various 2-oxazolines.

Reactions of a pincer ligand 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine (pzpypzH) with Cu(NO3)2, Cu(ClO4)2, CuSO4, CuCl2 or CuI produced three dinuclear Cu(II) complexes [{Cu(NO3)}(μ-pzpypz)]2 (1), [{Cu(ClO4)}(μ-pzpypz)]2 (2), [Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH (3·2MeOH), one mononuclear Cu(II) complex [CuCl2(pzpypzH)] (4) and one trinuclear Cu(I)/Cu(II) complex [(ICu)(μ-I)2Cu2(μ-pzpypz)2] (5), respectively. Treatment of 4 with two equiv. of AgNO3 in DMF also gave rise to 1. Complexes 1–5 were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 or 2 has a dimeric structure in which two {Cu(X)} (X = NO3, ClO4) fragments are interconnected by two μ-pzpypz− ligands. 3 also adopts a dimeric structure in which two Cu(II) centers are interconnected by a pair of μ-pzpypz− ligands and one μ-SO42− ion. The Cu(II) center in 4 is five-coordinated by three N atoms of the pzpypzH ligand and two Cl atoms. In 5, two Cu(II) centers are bridged by two μ-pzpypz− ligands and one CuI32− unit, forming a unique trinuclear structure. Complexes 1–5 displayed high catalytic activity toward the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes in H2O. The nitrile or aldehyde products could be readily separated from the catalytic system by extraction and the residual aqueous solution containing 1 retained good activity for several cycles.